1. EXECUTIVE SUMMARY
- CVSS v4 7.1
- ATTENTION: Low attack complexity
- Vendor: Johnson Controls Inc.
- Equipment: iSTAR eX, iSTAR Edge, iSTAR Ultra LT, iSTAR Ultra, iSTAR Ultra SE
- Vulnerability: Improper Validation of Certificate Expiration
2. RISK EVALUATION
Successful exploitation of this vulnerability could result in the product failing to re-establish communication once the certificate expires.
3. TECHNICAL DETAILS
3.1 AFFECTED PRODUCTS
The following versions of Johnson Controls iSTAR are affected:
- iSTAR eX: All versions prior to TLS 1.2
- iSTAR Edge: All versions prior to TLS 1.2
- iSTAR Ultra LT (if in TLS 1.2): All versions prior to TLS 1.2
- iSTAR Ultra (if in TLS 1.2): All versions prior to TLS 1.2
- iSTAR Ultra SE (if in TLS 1.2): All versions prior to TLS 1.2
3.2 VULNERABILITY OVERVIEW
3.2.1 IMPROPER VALIDATION OF CERTIFICATE EXPIRATION CWE-298
Under certain circumstances, an iSTAR using the default certificate to connect to the C•CURE Server may fail to re-establish communication, once the certificate expires.
CVE-2025-61736 has been assigned to this vulnerability. A CVSS v3.1 base score of 6.5 has been calculated; the CVSS vector string is (AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).
A CVSS v4 score has also been calculated for CVE-2025-61736. A base score of 7.1 has been calculated; the CVSS vector string is (AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N).
3.3 BACKGROUND
- CRITICAL INFRASTRUCTURE SECTORS: Commercial Facilities, Critical Manufacturing, Energy, Government Facilities, Transportation Systems
- COUNTRIES/AREAS DEPLOYED: Worldwide
- COMPANY HEADQUARTERS LOCATION: Ireland
3.4 RESEARCHER
Johnson Controls reported this vulnerability to CISA.
4. MITIGATIONS
Johnson Controls recommends the following mitigations:
Host-based certificates using TLS 1.2:
- Quickest solution
- No Upgrade required to specific C•CURE or iSTAR software/firmware versions
- Requires downloading a new certificate to all iSTAR panels simultaneously, resulting in a brief system downtime
Convert encryption mode to TLS 1.3, per cluster:
- Requires firmware 6.9.0 or higher, and C•CURE 9000 v2.90 SP3 or higher
- Enables phased implementation by cluster, minimizing disruption
- Note: TLS 1.3 is not supported on iSTAR eX, iSTAR Edge, and iSTAR Ultra LT panels
Upgrade legacy panels to new G2 hardware:
- Recommended for smaller systems due to time constraints
- Applies primarily to iSTAR eX, iSTAR Edge, and iSTAR LT panels
Johnson Controls strongly encourages users to work with their Software House integrators to audit their systems and determine the most appropriate course of action. Johnson Control’s technical support team provides extensive documentation and instructional videos on the Support Portal, and hosts ongoing webinars covering both host-based certificate implementation and TLS 1.3 migration.
For more detailed mitigation instructions, please see Johnson Controls Product Security Advisory JCI-PSA-2025-12 at the following location: https://www.johnsoncontrols.com/trust-center/cybersecurity/security-advisories
CISA recommends users take defensive measures to minimize the risk of exploitation of this vulnerability, such as:
- Minimize network exposure for all control system devices and/or systems, ensuring they are not accessible from the Internet.
- Locate control system networks and remote devices behind firewalls and isolating them from business networks.
- When remote access is required, use more secure methods, such as Virtual Private Networks (VPNs), recognizing VPNs may have vulnerabilities and should be updated to the most current version available. Also recognize VPN is only as secure as the connected devices.
CISA reminds organizations to perform proper impact analysis and risk assessment prior to deploying defensive measures.
CISA also provides a section for control systems security recommended practices on the ICS webpage on cisa.gov/ics. Several CISA products detailing cyber defense best practices are available for reading and download, including Improving Industrial Control Systems Cybersecurity with Defense-in-Depth Strategies.
CISA encourages organizations to implement recommended cybersecurity strategies for proactive defense of ICS assets.
Additional mitigation guidance and recommended practices are publicly available on the ICS webpage at cisa.gov/ics in the technical information paper, ICS-TIP-12-146-01B–Targeted Cyber Intrusion Detection and Mitigation Strategies.
Organizations observing suspected malicious activity should follow established internal procedures and report findings to CISA for tracking and correlation against other incidents.
CISA also recommends users take the following measures to protect themselves from social engineering attacks:
No known public exploitation specifically targeting this vulnerability has been reported to CISA at this time. This vulnerability is not exploitable remotely.
5. UPDATE HISTORY
- December 04, 2025: Initial Republication of JCI-PSA-2025-12